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Date: Mon, 4 Oct 2010 13:00:14 +0200 From: Arnd Bergmann <arnd@...db.de> To: Thomas Gleixner <tglx@...utronix.de> Cc: LKML <linux-kernel@...r.kernel.org>, Rusty Russell <rusty@...tcorp.com.au>, Kay Sievers <kay.sievers@...y.org>, Brandon Philips <brandon@...p.org> Subject: Re: [BUG 2.6.36-rc6] list corruption in module_bug_finalize On Sunday 03 October 2010, Thomas Gleixner wrote: > Current mainline triggers a list corruption bug in > module_bug_finalize(). dmesg excerpt below. > > The corresponding code says: > > /* > * Strictly speaking this should have a spinlock to protect against > * traversals, but since we only traverse on BUG()s, a spinlock > * could potentially lead to deadlock and thus be counter-productive. > */ > list_add(&mod->bug_list, &module_bug_list); > > I can see the traversal problem vs. BUG(), but what's protecting the > list_add() ? BKL probably did, but is that true anymore ? BKL hasn't been in this code path since before git. I think this relatively recent change caused module_finalize to be called without module_mutex held: commit 75676500f8298f0ee89db12db97294883c4b768e Author: Rusty Russell <rusty@...tcorp.com.au> Date: Sat Jun 5 11:17:36 2010 -0600 module: make locking more fine-grained. Kay Sievers <kay.sievers@...y.org> reports that we still have some contention over module loading which is slowing boot. Linus also disliked a previous "drop lock and regrab" patch to fix the bne2 "gave up waiting for init of module libcrc32c" message. This is more ambitious: we only grab the lock where we need it. Signed-off-by: Rusty Russell <rusty@...tcorp.com.au> Cc: Brandon Philips <brandon@...p.org> Cc: Kay Sievers <kay.sievers@...y.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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